While broader needs in portable phones have created strong demand for higher functions such as camera functions and larger screens, there is also strong demand for smaller and thinner phones in terms of portability. Various structures have been proposed in response to these conflicting demands. The same applies to PDAs (Personal Digital Assistance: portable information terminals) and other such portable devices. Generally, in casing structures used for portable devices, resin components or metal components are loosely fitted together and are either fixed in place with pawls or the like, or are fixed in place or enclosed by screw-fastening. In many cases, a combination of these methods is used. A cushion or the like is also sometimes attached in order to prevent deformation in the external casing from reaching the interior. Since the key switch portion requires a configuration that does not transfer keystroke force to internal components, a keystroke frame is sometimes used to cover a shield frame commonly formed on the mounting substrate, or both surfaces of a rigid mounting substrate are sometimes used and the key switches are formed on the back surface. Sometimes configurations are adopted in which a metal casing is used and the key switches are attached on top of the casing. Furthermore, as described in Patent Document 1, a structure for bearing the switch load is sometimes provided.
[Patent Document 1] Japanese Patent Application Kokai Publication No. 2003-229938